1. Field of the Invention
The invention relates to a sectional form for connection with other sections by coupling, flanging or the like. The sectional form is inserted into the bore of the section to be connected and expanded therein so that a locking union results. The invention further relates to the method of manufacture of such forms and the method for their application.
2. Description of the Prior Art
The connecting of a hollow section with other sections by coupling or flanging is known in the art. The hollow sections generally are, tubular, and may have cylindrical, square, rectangular or other desired cross-sections. These tubular hollow sections are coupled to other tubular sections, or to solid or hollow rails, etc. If the materials, usually metal, of the hollow sections to be connected have low ductility values there is a danger that in the process of coupling or flanging cracks will develop, which permanently weaken the union of the sections. As these cracks are often not immediately recognized, such unions offer no assurance of operational safety.
A great many hollow section forms are manufactured by extrusion. For a variety of reasons, the surface of the extruded products are provided with grooves or ribs, used for example for receiving screws or for increasing rigidity. When applying the fluted surfaces by coupling or flanging, there necessarily forms at the groove troughs or at the rib flanks weakened zones which lead to premature tearing during the shaping process. In the coupling process the grooves or ribs are expanded and therefore stretched, thus causing the material required for the process of coupling or flanging to be taken out of the wall thickness of the hollow section; this may encourage tearing during the coupling process.
It is also known to connect longitudinally welded pipes with other sections by coupling or flanging. In this case there is increased danger of tearing in the vicinity of the weld since imperfections at the weld may cause the material's extensibility to be exceeded. Difficulties of this type with aluminum ladder rungs have led to special designs where the connection is made possible by a center ridge inside the section for receiving a screw (see for example, German Utility Model DE-Gm 77 37 792). The present invention overcomes the problems of the prior art by providing the wall of the sectional shape with corrugations the total length of which correspond substantially to the periphery of the sectional form as applied by coupling or flanging.